The stepper/ball screw/support assemblies were ready to be attached to the machine. I used some K clamps across the width of the machine to use as supports to lay the assemblies on while I worked on aligning them properly.
First, I determined the front-back positioning. Moving the gantry to one end of travel, and the ball nut to the same end of its travel, I aligned the center of the ball nut coupler with the center point between the X linear bearing blocks. Then I clamped the assembly in place on that end. Moving the gantry and ball nut to the other end of their travel, I aligned the ball nut coupler with the center of the linear bearing blocks and measured the extra travel available on the ball screw. I split this measurement in half to allow equal space on both ends. I readjusted the position accordingly on both ends and clamped in place again.
To get the vertical alignment correct, I mounted the wooden piece to the ball nut coupler that would attach to the gantry. I moved one end up to the gantry, readjusting the k-clamp to set the new height, re-clamped the assembly, and then moved the ball nut and gantry back to the other end and repeated.
With everything in place and aligned, I unclamped one end at a time, applied wood glue, and re-clamped.
I then repeated the whole process for the second X axis drive assembly on the other side of the machine. After the glue was dry and I reconfirmed the alignment was still correct, I glued the pieces in place that attach the ball nut couplers to the gantry.
With the gantry mounted and the rails bonded in place, I was able to fine tune the X axis rail alignment. I loosened the linear bearings on one rail and attached a dial indicator to the gantry at that same end, reading to the reference edge of the profile rail. I ran the gantry back and forth to see how far out it was across the whole range of motion. Most of the rail was within +/- 0.001” parallel to the opposite rail. Toward the end there was a 6 inch section that was out by 8-10 thousandths. I loosened those rail mounting bolts and applied some pressure on the rail by hand to bring it back to zero before re-tightening the rail. After rechecking the whole rail it still needed some minor adjustments. After a few rounds of this I am happy with the straightness. Next up will be mounting the X axis drive assemblies.
After placing the linear guide blocks on the X rails, I placed the gantry on top of them and proceeded to align everything. I spent a lot of time aligning the X axis rails. This included making sure they were parallel with each other and also that they were perpendicular to the Y axis rails on the gantry. I clamped together a few 24” squares to get the rails parallel and then placed some 1-2-3 blocks on top of them to check that the Y axis rails were perpendicular. I clamped the rails in place as I went to keep the alignment correct. Once I was happy with everything, I marked out where the linear bearings should be mounted to the gantry. I drilled the gantry and mounted the linear bearings, then installed the gantry on the rails again. I forgot to mention that I had previously found the balance point of the gantry using a thin piece of wood running the long way under the gantry. I marked that balance point on the base of the gantry on both ends and that became the center point between the two linear bearings.
The alignment was double and triple checked prior to bonding the rails in place with the System Three adhesive epoxy. I still have some adjustment available in the rails to make fine adjustments with a dial indicator. I had previously used a chemical etch on these pieces of bar stock, but the epoxy should be applied very soon after the etching to get a good bond. I had let too much time pass and since I am experimenting and learning here, I decided to use the “wipe down with acetone” method for this to evaluate how the bond holds up compared to the other axes where I used the etching and sanding methods.
With the Z and Y Axis components almost complete, I couldn’t wait to get the X frame components built up. I cut all the plywood pieces on the tablesaw, then figured out what angle to cut out the MDF webs. Once I made one that fit well, I used the waste piece with a stop on my cross cut sled to quickly cut out the rest of the webs:
I assembled these in place on the machine base and once again glued everything up and used a lot of clamps. The waste pieces from the MDF webs came in handy again to make a squared up clamping surface.